xref: /dragonfly/sys/net/pf/pf_norm.c (revision b272101a)
1 /*	$OpenBSD: pf_norm.c,v 1.113 2008/05/07 07:07:29 markus Exp $ */
2 
3 /*
4  * Copyright (c) 2010 The DragonFly Project.  All rights reserved.
5  *
6  * Copyright 2001 Niels Provos <provos@citi.umich.edu>
7  * All rights reserved.
8  *
9  * Redistribution and use in source and binary forms, with or without
10  * modification, are permitted provided that the following conditions
11  * are met:
12  * 1. Redistributions of source code must retain the above copyright
13  *    notice, this list of conditions and the following disclaimer.
14  * 2. Redistributions in binary form must reproduce the above copyright
15  *    notice, this list of conditions and the following disclaimer in the
16  *    documentation and/or other materials provided with the distribution.
17  *
18  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
19  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
20  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
21  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
22  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
23  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
24  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
25  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
27  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28  */
29 
30 #include "opt_inet.h"
31 #include "opt_inet6.h"
32 
33 #include <sys/param.h>
34 #include <sys/systm.h>
35 #include <sys/mbuf.h>
36 #include <sys/filio.h>
37 #include <sys/fcntl.h>
38 #include <sys/malloc.h>
39 #include <sys/socket.h>
40 #include <sys/kernel.h>
41 #include <sys/time.h>
42 
43 #include <net/if.h>
44 #include <net/if_var.h>
45 #include <net/if_types.h>
46 #include <net/bpf.h>
47 #include <net/route.h>
48 #include <net/pf/if_pflog.h>
49 
50 #include <netinet/in.h>
51 #include <netinet/in_var.h>
52 #include <netinet/in_systm.h>
53 #include <netinet/ip.h>
54 #include <netinet/ip_var.h>
55 #include <netinet/tcp.h>
56 #include <netinet/tcp_seq.h>
57 #include <netinet/udp.h>
58 #include <netinet/ip_icmp.h>
59 
60 #ifdef INET6
61 #include <netinet/ip6.h>
62 #endif /* INET6 */
63 
64 #include <net/pf/pfvar.h>
65 
66 #define PFFRAG_SEENLAST	0x0001		/* Seen the last fragment for this */
67 #define PFFRAG_NOBUFFER	0x0002		/* Non-buffering fragment cache */
68 #define PFFRAG_DROP	0x0004		/* Drop all fragments */
69 #define BUFFER_FRAGMENTS(fr)	(!((fr)->fr_flags & PFFRAG_NOBUFFER))
70 
71 
72 TAILQ_HEAD(pf_fragqueue, pf_fragment)	*pf_fragqueue;
73 TAILQ_HEAD(pf_cachequeue, pf_fragment)	*pf_cachequeue;
74 
75 static __inline int	 pf_frag_compare(struct pf_fragment *,
76 			    struct pf_fragment *);
77 RB_HEAD(pf_frag_tree, pf_fragment)	*pf_frag_tree,
78 					*pf_cache_tree;
79 RB_PROTOTYPE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare);
80 RB_GENERATE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare);
81 
82 /* Private prototypes */
83 void			 pf_ip2key(struct pf_fragment *, struct ip *);
84 void			 pf_remove_fragment(struct pf_fragment *);
85 void			 pf_flush_fragments(void);
86 void			 pf_free_fragment(struct pf_fragment *);
87 struct pf_fragment	*pf_find_fragment(struct ip *, struct pf_frag_tree *);
88 struct mbuf		*pf_reassemble(struct mbuf **, struct pf_fragment **,
89 			    struct pf_frent *, int);
90 struct mbuf		*pf_fragcache(struct mbuf **, struct ip*,
91 			    struct pf_fragment **, int, int, int *);
92 int			 pf_normalize_tcpopt(struct pf_rule *, struct mbuf *,
93 			    struct tcphdr *, int, sa_family_t);
94 
95 #define	DPFPRINTF(x) do {				\
96 	if (pf_status.debug >= PF_DEBUG_MISC) {		\
97 		kprintf("%s: ", __func__);		\
98 		kprintf x ;				\
99 	}						\
100 } while(0)
101 
102 static MALLOC_DEFINE(M_PFFRAGPL, "pffrag", "pf fragment pool list");
103 static MALLOC_DEFINE(M_PFCACHEPL, "pffrcache", "pf fragment cache pool list");
104 static MALLOC_DEFINE(M_PFFRENTPL, "pffrent", "pf frent pool list");
105 static MALLOC_DEFINE(M_PFCENTPL, "pffrcent", "pf fragment cent pool list");
106 static MALLOC_DEFINE(M_PFSTATESCRUBPL, "pfstatescrub", "pf state scrub pool list");
107 
108 /* Globals */
109 struct malloc_type	 *pf_frent_pl, *pf_frag_pl, *pf_cache_pl, *pf_cent_pl;
110 struct malloc_type	 *pf_state_scrub_pl;
111 int			 pf_nfrents, pf_ncache;
112 
113 void
pf_normalize_init(void)114 pf_normalize_init(void)
115 {
116 	int n;
117 
118 	/* XXX
119 	pool_sethiwat(&pf_frag_pl, PFFRAG_FRAG_HIWAT);
120 	pool_sethardlimit(&pf_frent_pl, PFFRAG_FRENT_HIWAT, NULL, 0);
121 	pool_sethardlimit(&pf_cache_pl, PFFRAG_FRCACHE_HIWAT, NULL, 0);
122 	pool_sethardlimit(&pf_cent_pl, PFFRAG_FRCENT_HIWAT, NULL, 0);
123 	*/
124 
125 	/*
126 	 * pcpu queues and trees
127 	 */
128 	pf_fragqueue = kmalloc(sizeof(*pf_fragqueue) * ncpus,
129 				M_PF, M_WAITOK | M_ZERO);
130 	pf_cachequeue = kmalloc(sizeof(*pf_cachequeue) * ncpus,
131 				M_PF, M_WAITOK | M_ZERO);
132 	pf_frag_tree = kmalloc(sizeof(*pf_frag_tree) * ncpus,
133 				M_PF, M_WAITOK | M_ZERO);
134 	pf_cache_tree = kmalloc(sizeof(*pf_cache_tree) * ncpus,
135 				M_PF, M_WAITOK | M_ZERO);
136 
137 	for (n = 0; n < ncpus; ++n) {
138 		TAILQ_INIT(&pf_fragqueue[n]);
139 		TAILQ_INIT(&pf_cachequeue[n]);
140 		RB_INIT(&pf_frag_tree[n]);
141 		RB_INIT(&pf_cache_tree[n]);
142 	}
143 }
144 
145 void
pf_normalize_unload(void)146 pf_normalize_unload(void)
147 {
148 	kfree(pf_fragqueue, M_PF);
149 	kfree(pf_cachequeue, M_PF);
150 	kfree(pf_frag_tree, M_PF);
151 	kfree(pf_cache_tree, M_PF);
152 }
153 
154 static __inline int
pf_frag_compare(struct pf_fragment * a,struct pf_fragment * b)155 pf_frag_compare(struct pf_fragment *a, struct pf_fragment *b)
156 {
157 	int	diff;
158 
159 	if ((diff = a->fr_id - b->fr_id))
160 		return (diff);
161 	else if ((diff = a->fr_p - b->fr_p))
162 		return (diff);
163 	else if (a->fr_src.s_addr < b->fr_src.s_addr)
164 		return (-1);
165 	else if (a->fr_src.s_addr > b->fr_src.s_addr)
166 		return (1);
167 	else if (a->fr_dst.s_addr < b->fr_dst.s_addr)
168 		return (-1);
169 	else if (a->fr_dst.s_addr > b->fr_dst.s_addr)
170 		return (1);
171 	return (0);
172 }
173 
174 void
pf_purge_expired_fragments(void)175 pf_purge_expired_fragments(void)
176 {
177 	struct pf_fragment *frag;
178 	u_int32_t expire;
179 	int cpu = mycpu->gd_cpuid;
180 
181 	expire = time_second - pf_default_rule.timeout[PFTM_FRAG];
182 
183 	while ((frag = TAILQ_LAST(&pf_fragqueue[cpu], pf_fragqueue)) != NULL) {
184 		KASSERT((BUFFER_FRAGMENTS(frag)),
185 			("BUFFER_FRAGMENTS(frag) == 0: %s", __func__));
186 		if (frag->fr_timeout > expire)
187 			break;
188 
189 		DPFPRINTF(("expiring %d(%p)\n", frag->fr_id, frag));
190 		pf_free_fragment(frag);
191 	}
192 
193 	while ((frag = TAILQ_LAST(&pf_cachequeue[cpu], pf_cachequeue)) != NULL) {
194 		KASSERT((!BUFFER_FRAGMENTS(frag)),
195 			("BUFFER_FRAGMENTS(frag) != 0: %s", __func__));
196 		if (frag->fr_timeout > expire)
197 			break;
198 
199 		DPFPRINTF(("expiring %d(%p)\n", frag->fr_id, frag));
200 		pf_free_fragment(frag);
201 		KASSERT((TAILQ_EMPTY(&pf_cachequeue[cpu]) ||
202 		    TAILQ_LAST(&pf_cachequeue[cpu], pf_cachequeue) != frag),
203 		    ("!(TAILQ_EMPTY() || TAILQ_LAST() == farg): %s",
204 		    __func__));
205 	}
206 }
207 
208 /*
209  * Try to flush old fragments to make space for new ones
210  */
211 
212 void
pf_flush_fragments(void)213 pf_flush_fragments(void)
214 {
215 	struct pf_fragment *frag;
216 	int goal;
217 	int cpu = mycpu->gd_cpuid;
218 
219 	goal = pf_nfrents * 9 / 10;
220 	DPFPRINTF(("trying to free > %d frents\n",
221 	    pf_nfrents - goal));
222 	while (goal < pf_nfrents) {
223 		frag = TAILQ_LAST(&pf_fragqueue[cpu], pf_fragqueue);
224 		if (frag == NULL)
225 			break;
226 		pf_free_fragment(frag);
227 	}
228 
229 
230 	goal = pf_ncache * 9 / 10;
231 	DPFPRINTF(("trying to free > %d cache entries\n",
232 	    pf_ncache - goal));
233 	while (goal < pf_ncache) {
234 		frag = TAILQ_LAST(&pf_cachequeue[cpu], pf_cachequeue);
235 		if (frag == NULL)
236 			break;
237 		pf_free_fragment(frag);
238 	}
239 }
240 
241 /* Frees the fragments and all associated entries */
242 
243 void
pf_free_fragment(struct pf_fragment * frag)244 pf_free_fragment(struct pf_fragment *frag)
245 {
246 	struct pf_frent		*frent;
247 	struct pf_frcache	*frcache;
248 
249 	/* Free all fragments */
250 	if (BUFFER_FRAGMENTS(frag)) {
251 		for (frent = LIST_FIRST(&frag->fr_queue); frent;
252 		    frent = LIST_FIRST(&frag->fr_queue)) {
253 			LIST_REMOVE(frent, fr_next);
254 
255 			m_freem(frent->fr_m);
256 			kfree(frent, M_PFFRENTPL);
257 			pf_nfrents--;
258 		}
259 	} else {
260 		for (frcache = LIST_FIRST(&frag->fr_cache); frcache;
261 		    frcache = LIST_FIRST(&frag->fr_cache)) {
262 			LIST_REMOVE(frcache, fr_next);
263 
264 			KASSERT((LIST_EMPTY(&frag->fr_cache) ||
265 			    LIST_FIRST(&frag->fr_cache)->fr_off >
266 			    frcache->fr_end),
267 			    ("! (LIST_EMPTY() || LIST_FIRST()->fr_off >"
268                              " frcache->fr_end): %s", __func__));
269 
270 			kfree(frcache, M_PFCENTPL);
271 			pf_ncache--;
272 		}
273 	}
274 
275 	pf_remove_fragment(frag);
276 }
277 
278 void
pf_ip2key(struct pf_fragment * key,struct ip * ip)279 pf_ip2key(struct pf_fragment *key, struct ip *ip)
280 {
281 	key->fr_p = ip->ip_p;
282 	key->fr_id = ip->ip_id;
283 	key->fr_src.s_addr = ip->ip_src.s_addr;
284 	key->fr_dst.s_addr = ip->ip_dst.s_addr;
285 }
286 
287 struct pf_fragment *
pf_find_fragment(struct ip * ip,struct pf_frag_tree * tree)288 pf_find_fragment(struct ip *ip, struct pf_frag_tree *tree)
289 {
290 	struct pf_fragment	 key;
291 	struct pf_fragment	*frag;
292 	int cpu = mycpu->gd_cpuid;
293 
294 	pf_ip2key(&key, ip);
295 
296 	frag = RB_FIND(pf_frag_tree, tree, &key);
297 	if (frag != NULL) {
298 		/* XXX Are we sure we want to update the timeout? */
299 		frag->fr_timeout = time_second;
300 		if (BUFFER_FRAGMENTS(frag)) {
301 			TAILQ_REMOVE(&pf_fragqueue[cpu], frag, frag_next);
302 			TAILQ_INSERT_HEAD(&pf_fragqueue[cpu], frag, frag_next);
303 		} else {
304 			TAILQ_REMOVE(&pf_cachequeue[cpu], frag, frag_next);
305 			TAILQ_INSERT_HEAD(&pf_cachequeue[cpu], frag, frag_next);
306 		}
307 	}
308 
309 	return (frag);
310 }
311 
312 /* Removes a fragment from the fragment queue and frees the fragment */
313 
314 void
pf_remove_fragment(struct pf_fragment * frag)315 pf_remove_fragment(struct pf_fragment *frag)
316 {
317 	int cpu = mycpu->gd_cpuid;
318 
319 	if (BUFFER_FRAGMENTS(frag)) {
320 		RB_REMOVE(pf_frag_tree, &pf_frag_tree[cpu], frag);
321 		TAILQ_REMOVE(&pf_fragqueue[cpu], frag, frag_next);
322 		kfree(frag, M_PFFRAGPL);
323 	} else {
324 		RB_REMOVE(pf_frag_tree, &pf_cache_tree[cpu], frag);
325 		TAILQ_REMOVE(&pf_cachequeue[cpu], frag, frag_next);
326 		kfree(frag, M_PFCACHEPL);
327 	}
328 }
329 
330 #define FR_IP_OFF(fr)	((ntohs((fr)->fr_ip->ip_off) & IP_OFFMASK) << 3)
331 
332 struct mbuf *
pf_reassemble(struct mbuf ** m0,struct pf_fragment ** frag,struct pf_frent * frent,int mff)333 pf_reassemble(struct mbuf **m0, struct pf_fragment **frag,
334     struct pf_frent *frent, int mff)
335 {
336 	struct mbuf	*m = *m0, *m2;
337 	struct pf_frent	*frea, *next;
338 	struct pf_frent	*frep = NULL;
339 	struct ip	*ip = frent->fr_ip;
340 	int		hlen = ip->ip_hl << 2;
341 	u_int16_t	off = (ntohs(ip->ip_off) & IP_OFFMASK) << 3;
342 	u_int16_t	ip_len = ntohs(ip->ip_len) - hlen;
343 	u_int16_t	max = ip_len + off;
344 	int		cpu = mycpu->gd_cpuid;
345 
346 	KASSERT((*frag == NULL || BUFFER_FRAGMENTS(*frag)),
347 	    ("! (*frag == NULL || BUFFER_FRAGMENTS(*frag)): %s", __func__));
348 
349 	/* Strip off ip header */
350 	m->m_data += hlen;
351 	m->m_len -= hlen;
352 
353 	/* Create a new reassembly queue for this packet */
354 	if (*frag == NULL) {
355 		*frag = kmalloc(sizeof(struct pf_fragment),
356 				M_PFFRAGPL, M_NOWAIT);
357 		if (*frag == NULL) {
358 			pf_flush_fragments();
359 			*frag = kmalloc(sizeof(struct pf_fragment),
360 					M_PFFRAGPL, M_NOWAIT);
361 			if (*frag == NULL)
362 				goto drop_fragment;
363 		}
364 
365 		(*frag)->fr_flags = 0;
366 		(*frag)->fr_max = 0;
367 		(*frag)->fr_src = frent->fr_ip->ip_src;
368 		(*frag)->fr_dst = frent->fr_ip->ip_dst;
369 		(*frag)->fr_p = frent->fr_ip->ip_p;
370 		(*frag)->fr_id = frent->fr_ip->ip_id;
371 		(*frag)->fr_timeout = time_second;
372 		LIST_INIT(&(*frag)->fr_queue);
373 
374 		RB_INSERT(pf_frag_tree, &pf_frag_tree[cpu], *frag);
375 		TAILQ_INSERT_HEAD(&pf_fragqueue[cpu], *frag, frag_next);
376 
377 		/* We do not have a previous fragment */
378 		frep = NULL;
379 		goto insert;
380 	}
381 
382 	/*
383 	 * Find a fragment after the current one:
384 	 *  - off contains the real shifted offset.
385 	 */
386 	LIST_FOREACH(frea, &(*frag)->fr_queue, fr_next) {
387 		if (FR_IP_OFF(frea) > off)
388 			break;
389 		frep = frea;
390 	}
391 
392 	KASSERT((frep != NULL || frea != NULL),
393 	    ("!(frep != NULL || frea != NULL): %s", __func__));
394 
395 	/*
396 	 * Merge with previous fragment by cutting the start of
397 	 * the current packet.
398 	 */
399 	if (frep != NULL &&
400 	    (FR_IP_OFF(frep) + ntohs(frep->fr_ip->ip_len) -
401 	     frep->fr_ip->ip_hl * 4) > off)
402 	{
403 		u_int16_t	precut;
404 
405 		precut = FR_IP_OFF(frep) + ntohs(frep->fr_ip->ip_len) -
406 			 frep->fr_ip->ip_hl * 4 - off;
407 		if (precut >= ip_len)
408 			goto drop_fragment;
409 		m_adj(frent->fr_m, precut);
410 		DPFPRINTF(("overlap -%d\n", precut));
411 		/* Enforce 8 byte boundaries */
412 		ip->ip_off = htons(ntohs(ip->ip_off) + (precut >> 3));
413 		off = (ntohs(ip->ip_off) & IP_OFFMASK) << 3;
414 		ip_len -= precut;
415 		ip->ip_len = htons(ip_len + hlen);
416 	}
417 
418 	/*
419 	 * Cut or delete overlapping later fragments.
420 	 */
421 	for (; frea != NULL && ip_len + off > FR_IP_OFF(frea);
422 	    frea = next)
423 	{
424 		u_int16_t	aftercut;
425 
426 		aftercut = ip_len + off - FR_IP_OFF(frea);
427 		DPFPRINTF(("adjust overlap %d\n", aftercut));
428 		if (aftercut < (ntohs(frea->fr_ip->ip_len) -
429 				frea->fr_ip->ip_hl * 4))
430 		{
431 			frea->fr_ip->ip_len =
432 			    htons(ntohs(frea->fr_ip->ip_len) - aftercut +
433 				  frea->fr_ip->ip_hl * 4);
434 			frea->fr_ip->ip_off =
435 			    htons(ntohs(frea->fr_ip->ip_off) + (aftercut >> 3));
436 			m_adj(frea->fr_m, aftercut);
437 			break;
438 		}
439 
440 		/* This fragment is completely overlapped, lose it */
441 		next = LIST_NEXT(frea, fr_next);
442 		m_freem(frea->fr_m);
443 		LIST_REMOVE(frea, fr_next);
444 		kfree(frea, M_PFFRENTPL);
445 		pf_nfrents--;
446 	}
447 
448  insert:
449 	/* Update maximum data size */
450 	if ((*frag)->fr_max < max)
451 		(*frag)->fr_max = max;
452 	/* This is the last segment */
453 	if (!mff)
454 		(*frag)->fr_flags |= PFFRAG_SEENLAST;
455 
456 	if (frep == NULL)
457 		LIST_INSERT_HEAD(&(*frag)->fr_queue, frent, fr_next);
458 	else
459 		LIST_INSERT_AFTER(frep, frent, fr_next);
460 
461 	/* Check if we are completely reassembled */
462 	if (!((*frag)->fr_flags & PFFRAG_SEENLAST))
463 		return (NULL);
464 
465 	/* Check if we have all the data */
466 	off = 0;
467 	for (frep = LIST_FIRST(&(*frag)->fr_queue); frep; frep = next) {
468 		next = LIST_NEXT(frep, fr_next);
469 
470 		off += ntohs(frep->fr_ip->ip_len) - frep->fr_ip->ip_hl * 4;
471 		if (off < (*frag)->fr_max &&
472 		    (next == NULL || FR_IP_OFF(next) != off))
473 		{
474 			DPFPRINTF(("missing fragment at %d, next %d, max %d\n",
475 			    off, next == NULL ? -1 : FR_IP_OFF(next),
476 			    (*frag)->fr_max));
477 			return (NULL);
478 		}
479 	}
480 	DPFPRINTF(("%d < %d?\n", off, (*frag)->fr_max));
481 	if (off < (*frag)->fr_max)
482 		return (NULL);
483 
484 	/* We have all the data */
485 	frent = LIST_FIRST(&(*frag)->fr_queue);
486 	KASSERT((frent != NULL), ("frent == NULL: %s", __func__));
487 	if ((frent->fr_ip->ip_hl << 2) + off > IP_MAXPACKET) {
488 		DPFPRINTF(("drop: too big: %d\n", off));
489 		pf_free_fragment(*frag);
490 		*frag = NULL;
491 		return (NULL);
492 	}
493 	next = LIST_NEXT(frent, fr_next);
494 
495 	/* Magic from ip_input */
496 	ip = frent->fr_ip;
497 	m = frent->fr_m;
498 	m2 = m->m_next;
499 	m->m_next = NULL;
500 	m_cat(m, m2);
501 	kfree(frent, M_PFFRENTPL);
502 	pf_nfrents--;
503 	for (frent = next; frent != NULL; frent = next) {
504 		next = LIST_NEXT(frent, fr_next);
505 
506 		m2 = frent->fr_m;
507 		kfree(frent, M_PFFRENTPL);
508 		pf_nfrents--;
509 		m_cat(m, m2);
510 	}
511 
512 	ip->ip_src = (*frag)->fr_src;
513 	ip->ip_dst = (*frag)->fr_dst;
514 
515 	/* Remove from fragment queue */
516 	pf_remove_fragment(*frag);
517 	*frag = NULL;
518 
519 	hlen = ip->ip_hl << 2;
520 	ip->ip_len = htons(off + hlen);
521 	ip->ip_off &= htons(IP_DF);
522 	m->m_len += hlen;
523 	m->m_data -= hlen;
524 
525 	/* some debugging cruft by sklower, below, will go away soon */
526 	/* XXX this should be done elsewhere */
527 	if (m->m_flags & M_PKTHDR) {
528 		int plen = 0;
529 		for (m2 = m; m2; m2 = m2->m_next)
530 			plen += m2->m_len;
531 		m->m_pkthdr.len = plen;
532 	}
533 
534 #if 0
535 	kprintf("reassembly complete: len=%u\n", ntohs(ip->ip_len));
536 	kprintf("ip_src=%08x dst=%08x tos=%u p=%u off=%u len=%u\n",
537 		ip->ip_src.s_addr, ip->ip_dst.s_addr, ip->ip_tos, ip->ip_p,
538 		ntohs(ip->ip_off), ntohs(ip->ip_len));
539 #endif
540 
541 	DPFPRINTF(("complete: %p(%d)\n", m, ntohs(ip->ip_len)));
542 	return (m);
543 
544  drop_fragment:
545 	/* Oops - fail safe - drop packet */
546 	kfree(frent, M_PFFRENTPL);
547 	pf_nfrents--;
548 	m_freem(m);
549 	return (NULL);
550 }
551 
552 struct mbuf *
pf_fragcache(struct mbuf ** m0,struct ip * h,struct pf_fragment ** frag,int mff,int drop,int * nomem)553 pf_fragcache(struct mbuf **m0, struct ip *h, struct pf_fragment **frag, int mff,
554     int drop, int *nomem)
555 {
556 	struct mbuf	*m = *m0;
557 	struct pf_frcache *frp, *fra, *cur = NULL;
558 	int		ip_len = ntohs(h->ip_len) - (h->ip_hl << 2);
559 	u_int16_t	off = (ntohs(h->ip_off) & IP_OFFMASK) << 3;
560 	u_int16_t	max = ip_len + off;
561 	int		hosed = 0;
562 	int		cpu = mycpu->gd_cpuid;
563 
564 	KASSERT((*frag == NULL || !BUFFER_FRAGMENTS(*frag)),
565 	    ("!(*frag == NULL || !BUFFER_FRAGMENTS(*frag)): %s", __func__));
566 
567 	/* Create a new range queue for this packet */
568 	if (*frag == NULL) {
569 		*frag = kmalloc(sizeof(struct pf_fragment), M_PFCACHEPL, M_NOWAIT);
570 		if (*frag == NULL) {
571 			pf_flush_fragments();
572 			*frag = kmalloc(sizeof(struct pf_fragment), M_PFCACHEPL, M_NOWAIT);
573 			if (*frag == NULL)
574 				goto no_mem;
575 		}
576 
577 		/* Get an entry for the queue */
578 		cur = kmalloc(sizeof(struct pf_frcache), M_PFCENTPL, M_NOWAIT);
579 		if (cur == NULL) {
580 			kfree(*frag, M_PFCACHEPL);
581 			*frag = NULL;
582 			goto no_mem;
583 		}
584 		pf_ncache++;
585 
586 		(*frag)->fr_flags = PFFRAG_NOBUFFER;
587 		(*frag)->fr_max = 0;
588 		(*frag)->fr_src = h->ip_src;
589 		(*frag)->fr_dst = h->ip_dst;
590 		(*frag)->fr_p = h->ip_p;
591 		(*frag)->fr_id = h->ip_id;
592 		(*frag)->fr_timeout = time_second;
593 
594 		cur->fr_off = off;
595 		cur->fr_end = max;
596 		LIST_INIT(&(*frag)->fr_cache);
597 		LIST_INSERT_HEAD(&(*frag)->fr_cache, cur, fr_next);
598 
599 		RB_INSERT(pf_frag_tree, &pf_cache_tree[cpu], *frag);
600 		TAILQ_INSERT_HEAD(&pf_cachequeue[cpu], *frag, frag_next);
601 
602 		DPFPRINTF(("fragcache[%d]: new %d-%d\n", h->ip_id, off, max));
603 
604 		goto pass;
605 	}
606 
607 	/*
608 	 * Find a fragment after the current one:
609 	 *  - off contains the real shifted offset.
610 	 */
611 	frp = NULL;
612 	LIST_FOREACH(fra, &(*frag)->fr_cache, fr_next) {
613 		if (fra->fr_off > off)
614 			break;
615 		frp = fra;
616 	}
617 
618 	KASSERT((frp != NULL || fra != NULL),
619 	    ("!(frp != NULL || fra != NULL): %s", __func__));
620 
621 	if (frp != NULL) {
622 		int	precut;
623 
624 		precut = frp->fr_end - off;
625 		if (precut >= ip_len) {
626 			/* Fragment is entirely a duplicate */
627 			DPFPRINTF(("fragcache[%d]: dead (%d-%d) %d-%d\n",
628 			    h->ip_id, frp->fr_off, frp->fr_end, off, max));
629 			goto drop_fragment;
630 		}
631 		if (precut == 0) {
632 			/* They are adjacent.  Fixup cache entry */
633 			DPFPRINTF(("fragcache[%d]: adjacent (%d-%d) %d-%d\n",
634 			    h->ip_id, frp->fr_off, frp->fr_end, off, max));
635 			frp->fr_end = max;
636 		} else if (precut > 0) {
637 			/* The first part of this payload overlaps with a
638 			 * fragment that has already been passed.
639 			 * Need to trim off the first part of the payload.
640 			 * But to do so easily, we need to create another
641 			 * mbuf to throw the original header into.
642 			 */
643 
644 			DPFPRINTF(("fragcache[%d]: chop %d (%d-%d) %d-%d\n",
645 			    h->ip_id, precut, frp->fr_off, frp->fr_end, off,
646 			    max));
647 
648 			off += precut;
649 			max -= precut;
650 			/* Update the previous frag to encompass this one */
651 			frp->fr_end = max;
652 
653 			if (!drop) {
654 				/* XXX Optimization opportunity
655 				 * This is a very heavy way to trim the payload.
656 				 * we could do it much faster by diddling mbuf
657 				 * internals but that would be even less legible
658 				 * than this mbuf magic.  For my next trick,
659 				 * I'll pull a rabbit out of my laptop.
660 				 */
661 				*m0 = m_dup(m, M_NOWAIT);
662 				/* From KAME Project : We have missed this! */
663 				m_adj(*m0, (h->ip_hl << 2) -
664 				    (*m0)->m_pkthdr.len);
665 				if (*m0 == NULL)
666 					goto no_mem;
667 				KASSERT(((*m0)->m_next == NULL),
668 				    ("(*m0)->m_next != NULL: %s",
669 				    __func__));
670 				m_adj(m, precut + (h->ip_hl << 2));
671 				m_cat(*m0, m);
672 				m = *m0;
673 				if (m->m_flags & M_PKTHDR) {
674 					int plen = 0;
675 					struct mbuf *t;
676 					for (t = m; t; t = t->m_next)
677 						plen += t->m_len;
678 					m->m_pkthdr.len = plen;
679 				}
680 
681 
682 				h = mtod(m, struct ip *);
683 
684 				KASSERT(((int)m->m_len ==
685 				    ntohs(h->ip_len) - precut),
686 				    ("m->m_len != h->ip_len - precut: %s",
687 				    __func__));
688 				h->ip_off = htons(ntohs(h->ip_off) +
689 						  (precut >> 3));
690 				h->ip_len = htons(ntohs(h->ip_len) - precut);
691 			} else {
692 				hosed++;
693 			}
694 		} else {
695 			/* There is a gap between fragments */
696 
697 			DPFPRINTF(("fragcache[%d]: gap %d (%d-%d) %d-%d\n",
698 			    h->ip_id, -precut, frp->fr_off, frp->fr_end, off,
699 			    max));
700 
701 			cur = kmalloc(sizeof(struct pf_frcache), M_PFCENTPL, M_NOWAIT);
702 			if (cur == NULL)
703 				goto no_mem;
704 			pf_ncache++;
705 
706 			cur->fr_off = off;
707 			cur->fr_end = max;
708 			LIST_INSERT_AFTER(frp, cur, fr_next);
709 		}
710 	}
711 
712 	if (fra != NULL) {
713 		int	aftercut;
714 		int	merge = 0;
715 
716 		aftercut = max - fra->fr_off;
717 		if (aftercut == 0) {
718 			/* Adjacent fragments */
719 			DPFPRINTF(("fragcache[%d]: adjacent %d-%d (%d-%d)\n",
720 			    h->ip_id, off, max, fra->fr_off, fra->fr_end));
721 			fra->fr_off = off;
722 			merge = 1;
723 		} else if (aftercut > 0) {
724 			/* Need to chop off the tail of this fragment */
725 			DPFPRINTF(("fragcache[%d]: chop %d %d-%d (%d-%d)\n",
726 			    h->ip_id, aftercut, off, max, fra->fr_off,
727 			    fra->fr_end));
728 			fra->fr_off = off;
729 			max -= aftercut;
730 
731 			merge = 1;
732 
733 			if (!drop) {
734 				m_adj(m, -aftercut);
735 				if (m->m_flags & M_PKTHDR) {
736 					int plen = 0;
737 					struct mbuf *t;
738 					for (t = m; t; t = t->m_next)
739 						plen += t->m_len;
740 					m->m_pkthdr.len = plen;
741 				}
742 				h = mtod(m, struct ip *);
743 				KASSERT(((int)m->m_len ==
744 					 ntohs(h->ip_len) - aftercut),
745 				    ("m->m_len != h->ip_len - aftercut: %s",
746 				    __func__));
747 				h->ip_len = htons(ntohs(h->ip_len) - aftercut);
748 			} else {
749 				hosed++;
750 			}
751 		} else if (frp == NULL) {
752 			/* There is a gap between fragments */
753 			DPFPRINTF(("fragcache[%d]: gap %d %d-%d (%d-%d)\n",
754 			    h->ip_id, -aftercut, off, max, fra->fr_off,
755 			    fra->fr_end));
756 
757 			cur = kmalloc(sizeof(struct pf_frcache), M_PFCENTPL, M_NOWAIT);
758 			if (cur == NULL)
759 				goto no_mem;
760 			pf_ncache++;
761 
762 			cur->fr_off = off;
763 			cur->fr_end = max;
764 			LIST_INSERT_BEFORE(fra, cur, fr_next);
765 		}
766 
767 
768 		/* Need to glue together two separate fragment descriptors */
769 		if (merge) {
770 			if (cur && fra->fr_off <= cur->fr_end) {
771 				/* Need to merge in a previous 'cur' */
772 				DPFPRINTF(("fragcache[%d]: adjacent(merge "
773 				    "%d-%d) %d-%d (%d-%d)\n",
774 				    h->ip_id, cur->fr_off, cur->fr_end, off,
775 				    max, fra->fr_off, fra->fr_end));
776 				fra->fr_off = cur->fr_off;
777 				LIST_REMOVE(cur, fr_next);
778 				kfree(cur, M_PFCENTPL);
779 				pf_ncache--;
780 				cur = NULL;
781 
782 			} else if (frp && fra->fr_off <= frp->fr_end) {
783 				/* Need to merge in a modified 'frp' */
784 				KASSERT((cur == NULL), ("cur != NULL: %s",
785 				    __func__));
786 				DPFPRINTF(("fragcache[%d]: adjacent(merge "
787 				    "%d-%d) %d-%d (%d-%d)\n",
788 				    h->ip_id, frp->fr_off, frp->fr_end, off,
789 				    max, fra->fr_off, fra->fr_end));
790 				fra->fr_off = frp->fr_off;
791 				LIST_REMOVE(frp, fr_next);
792 				kfree(frp, M_PFCENTPL);
793 				pf_ncache--;
794 				frp = NULL;
795 
796 			}
797 		}
798 	}
799 
800 	if (hosed) {
801 		/*
802 		 * We must keep tracking the overall fragment even when
803 		 * we're going to drop it anyway so that we know when to
804 		 * free the overall descriptor.  Thus we drop the frag late.
805 		 */
806 		goto drop_fragment;
807 	}
808 
809 
810  pass:
811 	/* Update maximum data size */
812 	if ((*frag)->fr_max < max)
813 		(*frag)->fr_max = max;
814 
815 	/* This is the last segment */
816 	if (!mff)
817 		(*frag)->fr_flags |= PFFRAG_SEENLAST;
818 
819 	/* Check if we are completely reassembled */
820 	if (((*frag)->fr_flags & PFFRAG_SEENLAST) &&
821 	    LIST_FIRST(&(*frag)->fr_cache)->fr_off == 0 &&
822 	    LIST_FIRST(&(*frag)->fr_cache)->fr_end == (*frag)->fr_max) {
823 		/* Remove from fragment queue */
824 		DPFPRINTF(("fragcache[%d]: done 0-%d\n", h->ip_id,
825 		    (*frag)->fr_max));
826 		pf_free_fragment(*frag);
827 		*frag = NULL;
828 	}
829 
830 	return (m);
831 
832  no_mem:
833 	*nomem = 1;
834 
835 	/* Still need to pay attention to !IP_MF */
836 	if (!mff && *frag != NULL)
837 		(*frag)->fr_flags |= PFFRAG_SEENLAST;
838 
839 	m_freem(m);
840 	return (NULL);
841 
842  drop_fragment:
843 
844 	/* Still need to pay attention to !IP_MF */
845 	if (!mff && *frag != NULL)
846 		(*frag)->fr_flags |= PFFRAG_SEENLAST;
847 
848 	if (drop) {
849 		/* This fragment has been deemed bad.  Don't reass */
850 		if (((*frag)->fr_flags & PFFRAG_DROP) == 0)
851 			DPFPRINTF(("fragcache[%d]: dropping overall fragment\n",
852 			    h->ip_id));
853 		(*frag)->fr_flags |= PFFRAG_DROP;
854 	}
855 
856 	m_freem(m);
857 	return (NULL);
858 }
859 
860 int
pf_normalize_ip(struct mbuf ** m0,int dir,struct pfi_kif * kif,u_short * reason,struct pf_pdesc * pd)861 pf_normalize_ip(struct mbuf **m0, int dir, struct pfi_kif *kif, u_short *reason,
862     struct pf_pdesc *pd)
863 {
864 	struct mbuf	*m = *m0;
865 	struct pf_rule	*r;
866 	struct pf_frent	*frent;
867 	struct pf_fragment *frag = NULL;
868 	struct ip	*h = mtod(m, struct ip *);
869 	int		mff = (h->ip_off & htons(IP_MF));
870 	int		hlen = h->ip_hl << 2;
871 	u_int16_t	fragoff = (ntohs(h->ip_off) & IP_OFFMASK) << 3;
872 	u_int16_t	max;
873 	int		ip_len;
874 	int		tag = -1;
875 	int		cpu = mycpu->gd_cpuid;
876 
877 	r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr);
878 	while (r != NULL) {
879 		r->evaluations++;
880 		if (pfi_kif_match(r->kif, kif) == r->ifnot)
881 			r = r->skip[PF_SKIP_IFP].ptr;
882 		else if (r->direction && r->direction != dir)
883 			r = r->skip[PF_SKIP_DIR].ptr;
884 		else if (r->af && r->af != AF_INET)
885 			r = r->skip[PF_SKIP_AF].ptr;
886 		else if (r->proto && r->proto != h->ip_p)
887 			r = r->skip[PF_SKIP_PROTO].ptr;
888 		else if (PF_MISMATCHAW(&r->src.addr,
889 		    (struct pf_addr *)&h->ip_src.s_addr, AF_INET,
890 		    r->src.neg, kif))
891 			r = r->skip[PF_SKIP_SRC_ADDR].ptr;
892 		else if (PF_MISMATCHAW(&r->dst.addr,
893 		    (struct pf_addr *)&h->ip_dst.s_addr, AF_INET,
894 		    r->dst.neg, NULL))
895 			r = r->skip[PF_SKIP_DST_ADDR].ptr;
896 		else if (r->match_tag && !pf_match_tag(m, r, &tag))
897 			r = TAILQ_NEXT(r, entries);
898 		else
899 			break;
900 	}
901 
902 	if (r == NULL || r->action == PF_NOSCRUB)
903 		return (PF_PASS);
904 	else {
905 		r->packets[dir == PF_OUT]++;
906 		r->bytes[dir == PF_OUT] += pd->tot_len;
907 	}
908 
909 	/* Check for illegal packets */
910 	if (hlen < (int)sizeof(struct ip))
911 		goto drop;
912 
913 	if (hlen > ntohs(h->ip_len))
914 		goto drop;
915 
916 	/* Clear IP_DF if the rule uses the no-df option */
917 	if ((r->rule_flag & PFRULE_NODF) && (h->ip_off & htons(IP_DF))) {
918 		u_int16_t ip_off = h->ip_off;	/* network byte order */
919 
920 		h->ip_off &= ~htons(IP_DF);
921 		h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0);
922 	}
923 
924 	/* We will need other tests here */
925 	if (!fragoff && !mff)
926 		goto no_fragment;
927 
928 	/* A fragment; rehash required. */
929 	m->m_flags &= ~M_HASH;
930 
931 	/* We're dealing with a fragment now. Don't allow fragments
932 	 * with IP_DF to enter the cache. If the flag was cleared by
933 	 * no-df above, fine. Otherwise drop it.
934 	 */
935 	if (h->ip_off & htons(IP_DF)) {
936 		DPFPRINTF(("IP_DF\n"));
937 		goto bad;
938 	}
939 
940 	ip_len = ntohs(h->ip_len) - hlen;
941 
942 	/* All fragments are 8 byte aligned */
943 	if (mff && (ip_len & 0x7)) {
944 		DPFPRINTF(("mff and %d\n", ip_len));
945 		goto bad;
946 	}
947 
948 	/* Respect maximum length */
949 	if (fragoff + ip_len > IP_MAXPACKET) {
950 		DPFPRINTF(("max packet %d\n", fragoff + ip_len));
951 		goto bad;
952 	}
953 	max = fragoff + ip_len;
954 
955 	if ((r->rule_flag & (PFRULE_FRAGCROP|PFRULE_FRAGDROP)) == 0) {
956 		/* Fully buffer all of the fragments */
957 
958 		frag = pf_find_fragment(h, &pf_frag_tree[cpu]);
959 
960 		/* Check if we saw the last fragment already */
961 		if (frag != NULL && (frag->fr_flags & PFFRAG_SEENLAST) &&
962 		    max > frag->fr_max)
963 			goto bad;
964 
965 		/* Get an entry for the fragment queue */
966 		frent = kmalloc(sizeof(struct pf_frent), M_PFFRENTPL, M_NOWAIT);
967 		if (frent == NULL) {
968 			REASON_SET(reason, PFRES_MEMORY);
969 			return (PF_DROP);
970 		}
971 		pf_nfrents++;
972 		frent->fr_ip = h;
973 		frent->fr_m = m;
974 
975 		/* Might return a completely reassembled mbuf, or NULL */
976 		DPFPRINTF(("reass frag %d @ %d-%d\n", h->ip_id, fragoff, max));
977 		*m0 = m = pf_reassemble(m0, &frag, frent, mff);
978 
979 		if (m == NULL)
980 			return (PF_DROP);
981 
982 		if (frag != NULL && (frag->fr_flags & PFFRAG_DROP))
983 			goto drop;
984 
985 		h = mtod(m, struct ip *);
986 	} else {
987 		/* non-buffering fragment cache (drops or masks overlaps) */
988 		int	nomem = 0;
989 
990 		if (dir == PF_OUT && m->m_pkthdr.pf.flags & PF_TAG_FRAGCACHE) {
991 			/*
992 			 * Already passed the fragment cache in the
993 			 * input direction.  If we continued, it would
994 			 * appear to be a dup and would be dropped.
995 			 */
996 			goto fragment_pass;
997 		}
998 
999 		frag = pf_find_fragment(h, &pf_cache_tree[cpu]);
1000 
1001 		/* Check if we saw the last fragment already */
1002 		if (frag != NULL && (frag->fr_flags & PFFRAG_SEENLAST) &&
1003 		    max > frag->fr_max) {
1004 			if (r->rule_flag & PFRULE_FRAGDROP)
1005 				frag->fr_flags |= PFFRAG_DROP;
1006 			goto bad;
1007 		}
1008 
1009 		*m0 = m = pf_fragcache(m0, h, &frag, mff,
1010 		    (r->rule_flag & PFRULE_FRAGDROP) ? 1 : 0, &nomem);
1011 		if (m == NULL) {
1012 			if (nomem)
1013 				goto no_mem;
1014 			goto drop;
1015 		}
1016 
1017 		if (dir == PF_IN)
1018 			m->m_pkthdr.pf.flags |= PF_TAG_FRAGCACHE;
1019 
1020 		if (frag != NULL && (frag->fr_flags & PFFRAG_DROP))
1021 			goto drop;
1022 		goto fragment_pass;
1023 	}
1024 
1025  no_fragment:
1026 	/* At this point, only IP_DF is allowed in ip_off */
1027 	if (h->ip_off & ~htons(IP_DF)) {
1028 		u_int16_t ip_off = h->ip_off;	/* network byte order */
1029 
1030 		h->ip_off &= htons(IP_DF);
1031 		h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0);
1032 	}
1033 
1034 	/* Enforce a minimum ttl, may cause endless packet loops */
1035 	if (r->min_ttl && h->ip_ttl < r->min_ttl) {
1036 		u_int16_t ip_ttl = h->ip_ttl;
1037 
1038 		h->ip_ttl = r->min_ttl;
1039 		h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_ttl, h->ip_ttl, 0);
1040 	}
1041 
1042 	/* Enforce tos */
1043 	if (r->rule_flag & PFRULE_SET_TOS) {
1044 		u_int16_t	ov, nv;
1045 
1046 		ov = *(u_int16_t *)h;
1047 		h->ip_tos = r->set_tos;
1048 		nv = *(u_int16_t *)h;
1049 
1050 		h->ip_sum = pf_cksum_fixup(h->ip_sum, ov, nv, 0);
1051 	}
1052 
1053 	if (r->rule_flag & PFRULE_RANDOMID) {
1054 		u_int16_t ip_id = h->ip_id;
1055 
1056 		h->ip_id = ip_randomid();
1057 		h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_id, h->ip_id, 0);
1058 	}
1059 	if ((r->rule_flag & (PFRULE_FRAGCROP|PFRULE_FRAGDROP)) == 0)
1060 		pd->flags |= PFDESC_IP_REAS;
1061 
1062 	return (PF_PASS);
1063 
1064  fragment_pass:
1065 	/* Enforce a minimum ttl, may cause endless packet loops */
1066 	if (r->min_ttl && h->ip_ttl < r->min_ttl) {
1067 		u_int16_t ip_ttl = h->ip_ttl;
1068 
1069 		h->ip_ttl = r->min_ttl;
1070 		h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_ttl, h->ip_ttl, 0);
1071 	}
1072 	/* Enforce tos */
1073 	if (r->rule_flag & PFRULE_SET_TOS) {
1074 		u_int16_t	ov, nv;
1075 
1076 		ov = *(u_int16_t *)h;
1077 		h->ip_tos = r->set_tos;
1078 		nv = *(u_int16_t *)h;
1079 
1080 		h->ip_sum = pf_cksum_fixup(h->ip_sum, ov, nv, 0);
1081 	}
1082 	if ((r->rule_flag & (PFRULE_FRAGCROP|PFRULE_FRAGDROP)) == 0)
1083 		pd->flags |= PFDESC_IP_REAS;
1084 	return (PF_PASS);
1085 
1086  no_mem:
1087 	REASON_SET(reason, PFRES_MEMORY);
1088 	if (r != NULL && r->log)
1089 		PFLOG_PACKET(kif, h, m, AF_INET, dir, *reason, r, NULL, NULL, pd);
1090 	return (PF_DROP);
1091 
1092  drop:
1093 	REASON_SET(reason, PFRES_NORM);
1094 	if (r != NULL && r->log)
1095 		PFLOG_PACKET(kif, h, m, AF_INET, dir, *reason, r, NULL, NULL, pd);
1096 	return (PF_DROP);
1097 
1098  bad:
1099 	DPFPRINTF(("dropping bad fragment\n"));
1100 
1101 	/* Free associated fragments */
1102 	if (frag != NULL)
1103 		pf_free_fragment(frag);
1104 
1105 	REASON_SET(reason, PFRES_FRAG);
1106 	if (r != NULL && r->log)
1107 		PFLOG_PACKET(kif, h, m, AF_INET, dir, *reason, r, NULL, NULL, pd);
1108 
1109 	return (PF_DROP);
1110 }
1111 
1112 #ifdef INET6
1113 int
pf_normalize_ip6(struct mbuf ** m0,int dir,struct pfi_kif * kif,u_short * reason,struct pf_pdesc * pd)1114 pf_normalize_ip6(struct mbuf **m0, int dir, struct pfi_kif *kif,
1115     u_short *reason, struct pf_pdesc *pd)
1116 {
1117 	struct mbuf		*m = *m0;
1118 	struct pf_rule		*r;
1119 	struct ip6_hdr		*h = mtod(m, struct ip6_hdr *);
1120 	int			 off;
1121 	struct ip6_ext		 ext;
1122 	struct ip6_opt		 opt;
1123 	struct ip6_opt_jumbo	 jumbo;
1124 	struct ip6_frag		 frag;
1125 	u_int32_t		 jumbolen = 0, plen;
1126 	u_int16_t		 fragoff = 0;
1127 	int			 optend;
1128 	int			 ooff;
1129 	u_int8_t		 proto;
1130 	int			 terminal;
1131 
1132 	r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr);
1133 	while (r != NULL) {
1134 		r->evaluations++;
1135 		if (pfi_kif_match(r->kif, kif) == r->ifnot)
1136 			r = r->skip[PF_SKIP_IFP].ptr;
1137 		else if (r->direction && r->direction != dir)
1138 			r = r->skip[PF_SKIP_DIR].ptr;
1139 		else if (r->af && r->af != AF_INET6)
1140 			r = r->skip[PF_SKIP_AF].ptr;
1141 #if 0 /* header chain! */
1142 		else if (r->proto && r->proto != h->ip6_nxt)
1143 			r = r->skip[PF_SKIP_PROTO].ptr;
1144 #endif
1145 		else if (PF_MISMATCHAW(&r->src.addr,
1146 		    (struct pf_addr *)&h->ip6_src, AF_INET6,
1147 		    r->src.neg, kif))
1148 			r = r->skip[PF_SKIP_SRC_ADDR].ptr;
1149 		else if (PF_MISMATCHAW(&r->dst.addr,
1150 		    (struct pf_addr *)&h->ip6_dst, AF_INET6,
1151 		    r->dst.neg, NULL))
1152 			r = r->skip[PF_SKIP_DST_ADDR].ptr;
1153 		else
1154 			break;
1155 	}
1156 
1157 	if (r == NULL || r->action == PF_NOSCRUB)
1158 		return (PF_PASS);
1159 	else {
1160 		r->packets[dir == PF_OUT]++;
1161 		r->bytes[dir == PF_OUT] += pd->tot_len;
1162 	}
1163 
1164 	/* Check for illegal packets */
1165 	if (sizeof(struct ip6_hdr) + IPV6_MAXPACKET < m->m_pkthdr.len)
1166 		goto drop;
1167 
1168 	off = sizeof(struct ip6_hdr);
1169 	proto = h->ip6_nxt;
1170 	terminal = 0;
1171 	do {
1172 		switch (proto) {
1173 		case IPPROTO_FRAGMENT:
1174 			goto fragment;
1175 			break;
1176 		case IPPROTO_AH:
1177 		case IPPROTO_ROUTING:
1178 		case IPPROTO_DSTOPTS:
1179 			if (!pf_pull_hdr(m, off, &ext, sizeof(ext), NULL,
1180 			    NULL, AF_INET6))
1181 				goto shortpkt;
1182 			if (proto == IPPROTO_AH)
1183 				off += (ext.ip6e_len + 2) * 4;
1184 			else
1185 				off += (ext.ip6e_len + 1) * 8;
1186 			proto = ext.ip6e_nxt;
1187 			break;
1188 		case IPPROTO_HOPOPTS:
1189 			if (!pf_pull_hdr(m, off, &ext, sizeof(ext), NULL,
1190 			    NULL, AF_INET6))
1191 				goto shortpkt;
1192 			optend = off + (ext.ip6e_len + 1) * 8;
1193 			ooff = off + sizeof(ext);
1194 			do {
1195 				if (!pf_pull_hdr(m, ooff, &opt.ip6o_type,
1196 				    sizeof(opt.ip6o_type), NULL, NULL,
1197 				    AF_INET6))
1198 					goto shortpkt;
1199 				if (opt.ip6o_type == IP6OPT_PAD1) {
1200 					ooff++;
1201 					continue;
1202 				}
1203 				if (!pf_pull_hdr(m, ooff, &opt, sizeof(opt),
1204 				    NULL, NULL, AF_INET6))
1205 					goto shortpkt;
1206 				if (ooff + sizeof(opt) + opt.ip6o_len > optend)
1207 					goto drop;
1208 				switch (opt.ip6o_type) {
1209 				case IP6OPT_JUMBO:
1210 					if (h->ip6_plen != 0)
1211 						goto drop;
1212 					if (!pf_pull_hdr(m, ooff, &jumbo,
1213 					    sizeof(jumbo), NULL, NULL,
1214 					    AF_INET6))
1215 						goto shortpkt;
1216 					memcpy(&jumbolen, jumbo.ip6oj_jumbo_len,
1217 					    sizeof(jumbolen));
1218 					jumbolen = ntohl(jumbolen);
1219 					if (jumbolen <= IPV6_MAXPACKET)
1220 						goto drop;
1221 					if (sizeof(struct ip6_hdr) + jumbolen !=
1222 					    m->m_pkthdr.len)
1223 						goto drop;
1224 					break;
1225 				default:
1226 					break;
1227 				}
1228 				ooff += sizeof(opt) + opt.ip6o_len;
1229 			} while (ooff < optend);
1230 
1231 			off = optend;
1232 			proto = ext.ip6e_nxt;
1233 			break;
1234 		default:
1235 			terminal = 1;
1236 			break;
1237 		}
1238 	} while (!terminal);
1239 
1240 	/* jumbo payload option must be present, or plen > 0 */
1241 	if (ntohs(h->ip6_plen) == 0)
1242 		plen = jumbolen;
1243 	else
1244 		plen = ntohs(h->ip6_plen);
1245 	if (plen == 0)
1246 		goto drop;
1247 	if (sizeof(struct ip6_hdr) + plen > m->m_pkthdr.len)
1248 		goto shortpkt;
1249 
1250 	/* Enforce a minimum ttl, may cause endless packet loops */
1251 	if (r->min_ttl && h->ip6_hlim < r->min_ttl)
1252 		h->ip6_hlim = r->min_ttl;
1253 
1254 	return (PF_PASS);
1255 
1256  fragment:
1257 	if (ntohs(h->ip6_plen) == 0 || jumbolen)
1258 		goto drop;
1259 	plen = ntohs(h->ip6_plen);
1260 
1261 	if (!pf_pull_hdr(m, off, &frag, sizeof(frag), NULL, NULL, AF_INET6))
1262 		goto shortpkt;
1263 	fragoff = ntohs(frag.ip6f_offlg & IP6F_OFF_MASK);
1264 	if (fragoff + (plen - off - sizeof(frag)) > IPV6_MAXPACKET)
1265 		goto badfrag;
1266 
1267 	/* do something about it */
1268 	/* remember to set pd->flags |= PFDESC_IP_REAS */
1269 	return (PF_PASS);
1270 
1271  shortpkt:
1272 	REASON_SET(reason, PFRES_SHORT);
1273 	if (r != NULL && r->log)
1274 		PFLOG_PACKET(kif, h, m, AF_INET6, dir, *reason, r, NULL, NULL, pd);
1275 	return (PF_DROP);
1276 
1277  drop:
1278 	REASON_SET(reason, PFRES_NORM);
1279 	if (r != NULL && r->log)
1280 		PFLOG_PACKET(kif, h, m, AF_INET6, dir, *reason, r, NULL, NULL, pd);
1281 	return (PF_DROP);
1282 
1283  badfrag:
1284 	REASON_SET(reason, PFRES_FRAG);
1285 	if (r != NULL && r->log)
1286 		PFLOG_PACKET(kif, h, m, AF_INET6, dir, *reason, r, NULL, NULL, pd);
1287 	return (PF_DROP);
1288 }
1289 #endif /* INET6 */
1290 
1291 int
pf_normalize_tcp(int dir,struct pfi_kif * kif,struct mbuf * m,int ipoff,int off,void * h,struct pf_pdesc * pd)1292 pf_normalize_tcp(int dir, struct pfi_kif *kif, struct mbuf *m, int ipoff,
1293     int off, void *h, struct pf_pdesc *pd)
1294 {
1295 	struct pf_rule	*r, *rm = NULL;
1296 	struct tcphdr	*th = pd->hdr.tcp;
1297 	int		 rewrite = 0;
1298 	u_short		 reason;
1299 	u_int8_t	 flags;
1300 	sa_family_t	 af = pd->af;
1301 
1302 	r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr);
1303 	while (r != NULL) {
1304 		r->evaluations++;
1305 		if (pfi_kif_match(r->kif, kif) == r->ifnot)
1306 			r = r->skip[PF_SKIP_IFP].ptr;
1307 		else if (r->direction && r->direction != dir)
1308 			r = r->skip[PF_SKIP_DIR].ptr;
1309 		else if (r->af && r->af != af)
1310 			r = r->skip[PF_SKIP_AF].ptr;
1311 		else if (r->proto && r->proto != pd->proto)
1312 			r = r->skip[PF_SKIP_PROTO].ptr;
1313 		else if (PF_MISMATCHAW(&r->src.addr, pd->src, af,
1314 		    r->src.neg, kif))
1315 			r = r->skip[PF_SKIP_SRC_ADDR].ptr;
1316 		else if (r->src.port_op && !pf_match_port(r->src.port_op,
1317 			    r->src.port[0], r->src.port[1], th->th_sport))
1318 			r = r->skip[PF_SKIP_SRC_PORT].ptr;
1319 		else if (PF_MISMATCHAW(&r->dst.addr, pd->dst, af,
1320 		    r->dst.neg, NULL))
1321 			r = r->skip[PF_SKIP_DST_ADDR].ptr;
1322 		else if (r->dst.port_op && !pf_match_port(r->dst.port_op,
1323 			    r->dst.port[0], r->dst.port[1], th->th_dport))
1324 			r = r->skip[PF_SKIP_DST_PORT].ptr;
1325 		else if (r->os_fingerprint != PF_OSFP_ANY && !pf_osfp_match(
1326 			    pf_osfp_fingerprint(pd, m, off, th),
1327 			    r->os_fingerprint))
1328 			r = TAILQ_NEXT(r, entries);
1329 		else {
1330 			rm = r;
1331 			break;
1332 		}
1333 	}
1334 
1335 	if (rm == NULL || rm->action == PF_NOSCRUB)
1336 		return (PF_PASS);
1337 	else {
1338 		r->packets[dir == PF_OUT]++;
1339 		r->bytes[dir == PF_OUT] += pd->tot_len;
1340 	}
1341 
1342 	if (rm->rule_flag & PFRULE_REASSEMBLE_TCP)
1343 		pd->flags |= PFDESC_TCP_NORM;
1344 
1345 	flags = th->th_flags;
1346 	if (flags & TH_SYN) {
1347 		/* Illegal packet */
1348 		if (flags & TH_RST)
1349 			goto tcp_drop;
1350 
1351 		if (flags & TH_FIN)
1352 			flags &= ~TH_FIN;
1353 	} else {
1354 		/* Illegal packet */
1355 		if (!(flags & (TH_ACK|TH_RST)))
1356 			goto tcp_drop;
1357 	}
1358 
1359 	if (!(flags & TH_ACK)) {
1360 		/* These flags are only valid if ACK is set */
1361 		if ((flags & TH_FIN) || (flags & TH_PUSH) || (flags & TH_URG))
1362 			goto tcp_drop;
1363 	}
1364 
1365 	/* Check for illegal header length */
1366 	if (th->th_off < (sizeof(struct tcphdr) >> 2))
1367 		goto tcp_drop;
1368 
1369 	/* If flags changed, or reserved data set, then adjust */
1370 	if (flags != th->th_flags || th->th_x2 != 0) {
1371 		u_int16_t	ov, nv;
1372 
1373 		ov = *(u_int16_t *)(&th->th_ack + 1);
1374 		th->th_flags = flags;
1375 		th->th_x2 = 0;
1376 		nv = *(u_int16_t *)(&th->th_ack + 1);
1377 
1378 		th->th_sum = pf_cksum_fixup(th->th_sum, ov, nv, 0);
1379 		rewrite = 1;
1380 	}
1381 
1382 	/* Remove urgent pointer, if TH_URG is not set */
1383 	if (!(flags & TH_URG) && th->th_urp) {
1384 		th->th_sum = pf_cksum_fixup(th->th_sum, th->th_urp, 0, 0);
1385 		th->th_urp = 0;
1386 		rewrite = 1;
1387 	}
1388 
1389 	/* Process options */
1390 	if (r->max_mss && pf_normalize_tcpopt(r, m, th, off, pd->af))
1391 		rewrite = 1;
1392 
1393 	/* copy back packet headers if we sanitized */
1394 	if (rewrite)
1395 		m_copyback(m, off, sizeof(*th), th);
1396 
1397 	return (PF_PASS);
1398 
1399  tcp_drop:
1400 	REASON_SET(&reason, PFRES_NORM);
1401 	if (rm != NULL && r->log)
1402 		PFLOG_PACKET(kif, h, m, AF_INET, dir, reason, r, NULL, NULL, pd);
1403 	return (PF_DROP);
1404 }
1405 
1406 int
pf_normalize_tcp_init(struct mbuf * m,int off,struct pf_pdesc * pd,struct tcphdr * th,struct pf_state_peer * src,struct pf_state_peer * dst)1407 pf_normalize_tcp_init(struct mbuf *m, int off, struct pf_pdesc *pd,
1408     struct tcphdr *th, struct pf_state_peer *src, struct pf_state_peer *dst)
1409 {
1410 	u_int32_t tsval, tsecr;
1411 	u_int8_t hdr[60];
1412 	u_int8_t *opt;
1413 
1414 	KASSERT((src->scrub == NULL),
1415 	    ("pf_normalize_tcp_init: src->scrub != NULL"));
1416 
1417 	src->scrub = kmalloc(sizeof(struct pf_state_scrub), M_PFSTATESCRUBPL,
1418 	    M_NOWAIT | M_ZERO);
1419 	if (src->scrub == NULL)
1420 		return (1);
1421 
1422 	switch (pd->af) {
1423 #ifdef INET
1424 	case AF_INET: {
1425 		struct ip *h = mtod(m, struct ip *);
1426 		src->scrub->pfss_ttl = h->ip_ttl;
1427 		break;
1428 	}
1429 #endif /* INET */
1430 #ifdef INET6
1431 	case AF_INET6: {
1432 		struct ip6_hdr *h = mtod(m, struct ip6_hdr *);
1433 		src->scrub->pfss_ttl = h->ip6_hlim;
1434 		break;
1435 	}
1436 #endif /* INET6 */
1437 	}
1438 
1439 
1440 	/*
1441 	 * All normalizations below are only begun if we see the start of
1442 	 * the connections.  They must all set an enabled bit in pfss_flags
1443 	 */
1444 	if ((th->th_flags & TH_SYN) == 0)
1445 		return (0);
1446 
1447 
1448 	if (th->th_off > (sizeof(struct tcphdr) >> 2) && src->scrub &&
1449 	    pf_pull_hdr(m, off, hdr, th->th_off << 2, NULL, NULL, pd->af)) {
1450 		/* Diddle with TCP options */
1451 		int hlen;
1452 		opt = hdr + sizeof(struct tcphdr);
1453 		hlen = (th->th_off << 2) - sizeof(struct tcphdr);
1454 		while (hlen >= TCPOLEN_TIMESTAMP) {
1455 			switch (*opt) {
1456 			case TCPOPT_EOL:	/* FALLTHROUGH */
1457 			case TCPOPT_NOP:
1458 				opt++;
1459 				hlen--;
1460 				break;
1461 			case TCPOPT_TIMESTAMP:
1462 				if (opt[1] >= TCPOLEN_TIMESTAMP) {
1463 					src->scrub->pfss_flags |=
1464 					    PFSS_TIMESTAMP;
1465 					src->scrub->pfss_ts_mod = karc4random();
1466 
1467 					/* note PFSS_PAWS not set yet */
1468 					memcpy(&tsval, &opt[2],
1469 					    sizeof(u_int32_t));
1470 					memcpy(&tsecr, &opt[6],
1471 					    sizeof(u_int32_t));
1472 					src->scrub->pfss_tsval0 = ntohl(tsval);
1473 					src->scrub->pfss_tsval = ntohl(tsval);
1474 					src->scrub->pfss_tsecr = ntohl(tsecr);
1475 					getmicrouptime(&src->scrub->pfss_last);
1476 				}
1477 				/* FALLTHROUGH */
1478 			default:
1479 				hlen -= MAX(opt[1], 2);
1480 				opt += MAX(opt[1], 2);
1481 				break;
1482 			}
1483 		}
1484 	}
1485 
1486 	return (0);
1487 }
1488 
1489 void
pf_normalize_tcp_cleanup(struct pf_state * state)1490 pf_normalize_tcp_cleanup(struct pf_state *state)
1491 {
1492 	if (state->src.scrub)
1493 		kfree(state->src.scrub, M_PFSTATESCRUBPL);
1494 	if (state->dst.scrub)
1495 		kfree(state->dst.scrub, M_PFSTATESCRUBPL);
1496 
1497 	/* Someday... flush the TCP segment reassembly descriptors. */
1498 }
1499 
1500 int
pf_normalize_tcp_stateful(struct mbuf * m,int off,struct pf_pdesc * pd,u_short * reason,struct tcphdr * th,struct pf_state * state,struct pf_state_peer * src,struct pf_state_peer * dst,int * writeback)1501 pf_normalize_tcp_stateful(struct mbuf *m, int off, struct pf_pdesc *pd,
1502     u_short *reason, struct tcphdr *th, struct pf_state *state,
1503     struct pf_state_peer *src, struct pf_state_peer *dst, int *writeback)
1504 {
1505 	struct timeval uptime;
1506 	u_int32_t tsval, tsecr;
1507 	u_int tsval_from_last;
1508 	u_int8_t hdr[60];
1509 	u_int8_t *opt;
1510 	int copyback = 0;
1511 	int got_ts = 0;
1512 
1513 	KASSERT((src->scrub || dst->scrub),
1514 	    ("pf_normalize_tcp_statefull: src->scrub && dst->scrub!"));
1515 
1516 	tsval = 0;	/* avoid gcc complaint */
1517 	tsecr = 0;	/* avoid gcc complaint */
1518 
1519 	/*
1520 	 * Enforce the minimum TTL seen for this connection.  Negate a common
1521 	 * technique to evade an intrusion detection system and confuse
1522 	 * firewall state code.
1523 	 */
1524 	switch (pd->af) {
1525 #ifdef INET
1526 	case AF_INET: {
1527 		if (src->scrub) {
1528 			struct ip *h = mtod(m, struct ip *);
1529 			if (h->ip_ttl > src->scrub->pfss_ttl)
1530 				src->scrub->pfss_ttl = h->ip_ttl;
1531 			h->ip_ttl = src->scrub->pfss_ttl;
1532 		}
1533 		break;
1534 	}
1535 #endif /* INET */
1536 #ifdef INET6
1537 	case AF_INET6: {
1538 		if (src->scrub) {
1539 			struct ip6_hdr *h = mtod(m, struct ip6_hdr *);
1540 			if (h->ip6_hlim > src->scrub->pfss_ttl)
1541 				src->scrub->pfss_ttl = h->ip6_hlim;
1542 			h->ip6_hlim = src->scrub->pfss_ttl;
1543 		}
1544 		break;
1545 	}
1546 #endif /* INET6 */
1547 	}
1548 
1549 	if (th->th_off > (sizeof(struct tcphdr) >> 2) &&
1550 	    ((src->scrub && (src->scrub->pfss_flags & PFSS_TIMESTAMP)) ||
1551 	    (dst->scrub && (dst->scrub->pfss_flags & PFSS_TIMESTAMP))) &&
1552 	    pf_pull_hdr(m, off, hdr, th->th_off << 2, NULL, NULL, pd->af)) {
1553 		/* Diddle with TCP options */
1554 		int hlen;
1555 		opt = hdr + sizeof(struct tcphdr);
1556 		hlen = (th->th_off << 2) - sizeof(struct tcphdr);
1557 		while (hlen >= TCPOLEN_TIMESTAMP) {
1558 			switch (*opt) {
1559 			case TCPOPT_EOL:	/* FALLTHROUGH */
1560 			case TCPOPT_NOP:
1561 				opt++;
1562 				hlen--;
1563 				break;
1564 			case TCPOPT_TIMESTAMP:
1565 				/* Modulate the timestamps.  Can be used for
1566 				 * NAT detection, OS uptime determination or
1567 				 * reboot detection.
1568 				 */
1569 
1570 				if (got_ts) {
1571 					/* Huh?  Multiple timestamps!? */
1572 					if (pf_status.debug >= PF_DEBUG_MISC) {
1573 						DPFPRINTF(("multiple TS??"));
1574 						pf_print_state(state);
1575 						kprintf("\n");
1576 					}
1577 					REASON_SET(reason, PFRES_TS);
1578 					return (PF_DROP);
1579 				}
1580 				if (opt[1] >= TCPOLEN_TIMESTAMP) {
1581 					memcpy(&tsval, &opt[2],
1582 					    sizeof(u_int32_t));
1583 					if (tsval && src->scrub &&
1584 					    (src->scrub->pfss_flags &
1585 					    PFSS_TIMESTAMP)) {
1586 						tsval = ntohl(tsval);
1587 						pf_change_a(&opt[2],
1588 						    &th->th_sum,
1589 						    htonl(tsval +
1590 						    src->scrub->pfss_ts_mod),
1591 						    0);
1592 						copyback = 1;
1593 					}
1594 
1595 					/* Modulate TS reply iff valid (!0) */
1596 					memcpy(&tsecr, &opt[6],
1597 					    sizeof(u_int32_t));
1598 					if (tsecr && dst->scrub &&
1599 					    (dst->scrub->pfss_flags &
1600 					    PFSS_TIMESTAMP)) {
1601 						tsecr = ntohl(tsecr)
1602 						    - dst->scrub->pfss_ts_mod;
1603 						pf_change_a(&opt[6],
1604 						    &th->th_sum, htonl(tsecr),
1605 						    0);
1606 						copyback = 1;
1607 					}
1608 					got_ts = 1;
1609 				}
1610 				/* FALLTHROUGH */
1611 			default:
1612 				hlen -= MAX(opt[1], 2);
1613 				opt += MAX(opt[1], 2);
1614 				break;
1615 			}
1616 		}
1617 		if (copyback) {
1618 			/* Copyback the options, caller copys back header */
1619 			*writeback = 1;
1620 			m_copyback(m, off + sizeof(struct tcphdr),
1621 			    (th->th_off << 2) - sizeof(struct tcphdr),
1622 			    hdr + sizeof(struct tcphdr));
1623 		}
1624 	}
1625 
1626 
1627 	/*
1628 	 * Must invalidate PAWS checks on connections idle for too long.
1629 	 * The fastest allowed timestamp clock is 1ms.  That turns out to
1630 	 * be about 24 days before it wraps.  XXX Right now our lowerbound
1631 	 * TS echo check only works for the first 12 days of a connection
1632 	 * when the TS has exhausted half its 32bit space
1633 	 */
1634 #define TS_MAX_IDLE	(24*24*60*60)
1635 #define TS_MAX_CONN	(12*24*60*60)	/* XXX remove when better tsecr check */
1636 
1637 	getmicrouptime(&uptime);
1638 	if (src->scrub && (src->scrub->pfss_flags & PFSS_PAWS) &&
1639 	    (uptime.tv_sec - src->scrub->pfss_last.tv_sec > TS_MAX_IDLE ||
1640 	    time_second - state->creation > TS_MAX_CONN))  {
1641 		if (pf_status.debug >= PF_DEBUG_MISC) {
1642 			DPFPRINTF(("src idled out of PAWS\n"));
1643 			pf_print_state(state);
1644 			kprintf("\n");
1645 		}
1646 		src->scrub->pfss_flags = (src->scrub->pfss_flags & ~PFSS_PAWS)
1647 		    | PFSS_PAWS_IDLED;
1648 	}
1649 	if (dst->scrub && (dst->scrub->pfss_flags & PFSS_PAWS) &&
1650 	    uptime.tv_sec - dst->scrub->pfss_last.tv_sec > TS_MAX_IDLE) {
1651 		if (pf_status.debug >= PF_DEBUG_MISC) {
1652 			DPFPRINTF(("dst idled out of PAWS\n"));
1653 			pf_print_state(state);
1654 			kprintf("\n");
1655 		}
1656 		dst->scrub->pfss_flags = (dst->scrub->pfss_flags & ~PFSS_PAWS)
1657 		    | PFSS_PAWS_IDLED;
1658 	}
1659 
1660 	if (got_ts && src->scrub && dst->scrub &&
1661 	    (src->scrub->pfss_flags & PFSS_PAWS) &&
1662 	    (dst->scrub->pfss_flags & PFSS_PAWS)) {
1663 		/* Validate that the timestamps are "in-window".
1664 		 * RFC1323 describes TCP Timestamp options that allow
1665 		 * measurement of RTT (round trip time) and PAWS
1666 		 * (protection against wrapped sequence numbers).  PAWS
1667 		 * gives us a set of rules for rejecting packets on
1668 		 * long fat pipes (packets that were somehow delayed
1669 		 * in transit longer than the time it took to send the
1670 		 * full TCP sequence space of 4Gb).  We can use these
1671 		 * rules and infer a few others that will let us treat
1672 		 * the 32bit timestamp and the 32bit echoed timestamp
1673 		 * as sequence numbers to prevent a blind attacker from
1674 		 * inserting packets into a connection.
1675 		 *
1676 		 * RFC1323 tells us:
1677 		 *  - The timestamp on this packet must be greater than
1678 		 *    or equal to the last value echoed by the other
1679 		 *    endpoint.  The RFC says those will be discarded
1680 		 *    since it is a dup that has already been acked.
1681 		 *    This gives us a lowerbound on the timestamp.
1682 		 *        timestamp >= other last echoed timestamp
1683 		 *  - The timestamp will be less than or equal to
1684 		 *    the last timestamp plus the time between the
1685 		 *    last packet and now.  The RFC defines the max
1686 		 *    clock rate as 1ms.  We will allow clocks to be
1687 		 *    up to 10% fast and will allow a total difference
1688 		 *    or 30 seconds due to a route change.  And this
1689 		 *    gives us an upperbound on the timestamp.
1690 		 *        timestamp <= last timestamp + max ticks
1691 		 *    We have to be careful here.  Windows will send an
1692 		 *    initial timestamp of zero and then initialize it
1693 		 *    to a random value after the 3whs; presumably to
1694 		 *    avoid a DoS by having to call an expensive RNG
1695 		 *    during a SYN flood.  Proof MS has at least one
1696 		 *    good security geek.
1697 		 *
1698 		 *  - The TCP timestamp option must also echo the other
1699 		 *    endpoints timestamp.  The timestamp echoed is the
1700 		 *    one carried on the earliest unacknowledged segment
1701 		 *    on the left edge of the sequence window.  The RFC
1702 		 *    states that the host will reject any echoed
1703 		 *    timestamps that were larger than any ever sent.
1704 		 *    This gives us an upperbound on the TS echo.
1705 		 *        tescr <= largest_tsval
1706 		 *  - The lowerbound on the TS echo is a little more
1707 		 *    tricky to determine.  The other endpoint's echoed
1708 		 *    values will not decrease.  But there may be
1709 		 *    network conditions that re-order packets and
1710 		 *    cause our view of them to decrease.  For now the
1711 		 *    only lowerbound we can safely determine is that
1712 		 *    the TS echo will never be less than the original
1713 		 *    TS.  XXX There is probably a better lowerbound.
1714 		 *    Remove TS_MAX_CONN with better lowerbound check.
1715 		 *        tescr >= other original TS
1716 		 *
1717 		 * It is also important to note that the fastest
1718 		 * timestamp clock of 1ms will wrap its 32bit space in
1719 		 * 24 days.  So we just disable TS checking after 24
1720 		 * days of idle time.  We actually must use a 12d
1721 		 * connection limit until we can come up with a better
1722 		 * lowerbound to the TS echo check.
1723 		 */
1724 		struct timeval delta_ts;
1725 		int ts_fudge;
1726 
1727 
1728 		/*
1729 		 * PFTM_TS_DIFF is how many seconds of leeway to allow
1730 		 * a host's timestamp.  This can happen if the previous
1731 		 * packet got delayed in transit for much longer than
1732 		 * this packet.
1733 		 */
1734 		if ((ts_fudge = state->rule.ptr->timeout[PFTM_TS_DIFF]) == 0)
1735 			ts_fudge = pf_default_rule.timeout[PFTM_TS_DIFF];
1736 
1737 
1738 		/* Calculate max ticks since the last timestamp */
1739 #define TS_MAXFREQ	1100		/* RFC max TS freq of 1Khz + 10% skew */
1740 #define TS_MICROSECS	1000000		/* microseconds per second */
1741 #ifndef timersub
1742 #define timersub(tvp, uvp, vvp)						\
1743 	do {								\
1744 		(vvp)->tv_sec = (tvp)->tv_sec - (uvp)->tv_sec;		\
1745 		(vvp)->tv_usec = (tvp)->tv_usec - (uvp)->tv_usec;	\
1746 		if ((vvp)->tv_usec < 0) {				\
1747 			(vvp)->tv_sec--;				\
1748 			(vvp)->tv_usec += 1000000;			\
1749 		}							\
1750 	} while (0)
1751 #endif
1752 
1753 		timersub(&uptime, &src->scrub->pfss_last, &delta_ts);
1754 		tsval_from_last = (delta_ts.tv_sec + ts_fudge) * TS_MAXFREQ;
1755 		tsval_from_last += delta_ts.tv_usec / (TS_MICROSECS/TS_MAXFREQ);
1756 
1757 
1758 		if ((src->state >= TCPS_ESTABLISHED &&
1759 		    dst->state >= TCPS_ESTABLISHED) &&
1760 		    (SEQ_LT(tsval, dst->scrub->pfss_tsecr) ||
1761 		    SEQ_GT(tsval, src->scrub->pfss_tsval + tsval_from_last) ||
1762 		    (tsecr && (SEQ_GT(tsecr, dst->scrub->pfss_tsval) ||
1763 		    SEQ_LT(tsecr, dst->scrub->pfss_tsval0))))) {
1764 			/* Bad RFC1323 implementation or an insertion attack.
1765 			 *
1766 			 * - Solaris 2.6 and 2.7 are known to send another ACK
1767 			 *   after the FIN,FIN|ACK,ACK closing that carries
1768 			 *   an old timestamp.
1769 			 */
1770 
1771 			DPFPRINTF(("Timestamp failed %c%c%c%c\n",
1772 			    SEQ_LT(tsval, dst->scrub->pfss_tsecr) ? '0' : ' ',
1773 			    SEQ_GT(tsval, src->scrub->pfss_tsval +
1774 			    tsval_from_last) ? '1' : ' ',
1775 			    SEQ_GT(tsecr, dst->scrub->pfss_tsval) ? '2' : ' ',
1776 			    SEQ_LT(tsecr, dst->scrub->pfss_tsval0)? '3' : ' '));
1777 			DPFPRINTF((" tsval: %u  tsecr: %u  +ticks: %u  "
1778 			    "idle: %lus %lums\n",
1779 			    tsval, tsecr, tsval_from_last, delta_ts.tv_sec,
1780 			    delta_ts.tv_usec / 1000));
1781 			DPFPRINTF((" src->tsval: %u  tsecr: %u\n",
1782 			    src->scrub->pfss_tsval, src->scrub->pfss_tsecr));
1783 			DPFPRINTF((" dst->tsval: %u  tsecr: %u  tsval0: %u"
1784 			    "\n", dst->scrub->pfss_tsval,
1785 			    dst->scrub->pfss_tsecr, dst->scrub->pfss_tsval0));
1786 			if (pf_status.debug >= PF_DEBUG_MISC) {
1787 				pf_print_state(state);
1788 				pf_print_flags(th->th_flags);
1789 				kprintf("\n");
1790 			}
1791 			REASON_SET(reason, PFRES_TS);
1792 			return (PF_DROP);
1793 		}
1794 
1795 		/* XXX I'd really like to require tsecr but it's optional */
1796 
1797 	} else if (!got_ts && (th->th_flags & TH_RST) == 0 &&
1798 	    ((src->state == TCPS_ESTABLISHED && dst->state == TCPS_ESTABLISHED)
1799 	    || pd->p_len > 0 || (th->th_flags & TH_SYN)) &&
1800 	    src->scrub && dst->scrub &&
1801 	    (src->scrub->pfss_flags & PFSS_PAWS) &&
1802 	    (dst->scrub->pfss_flags & PFSS_PAWS)) {
1803 		/* Didn't send a timestamp.  Timestamps aren't really useful
1804 		 * when:
1805 		 *  - connection opening or closing (often not even sent).
1806 		 *    but we must not let an attacker to put a FIN on a
1807 		 *    data packet to sneak it through our ESTABLISHED check.
1808 		 *  - on a TCP reset.  RFC suggests not even looking at TS.
1809 		 *  - on an empty ACK.  The TS will not be echoed so it will
1810 		 *    probably not help keep the RTT calculation in sync and
1811 		 *    there isn't as much danger when the sequence numbers
1812 		 *    got wrapped.  So some stacks don't include TS on empty
1813 		 *    ACKs :-(
1814 		 *
1815 		 * To minimize the disruption to mostly RFC1323 conformant
1816 		 * stacks, we will only require timestamps on data packets.
1817 		 *
1818 		 * And what do ya know, we cannot require timestamps on data
1819 		 * packets.  There appear to be devices that do legitimate
1820 		 * TCP connection hijacking.  There are HTTP devices that allow
1821 		 * a 3whs (with timestamps) and then buffer the HTTP request.
1822 		 * If the intermediate device has the HTTP response cache, it
1823 		 * will spoof the response but not bother timestamping its
1824 		 * packets.  So we can look for the presence of a timestamp in
1825 		 * the first data packet and if there, require it in all future
1826 		 * packets.
1827 		 */
1828 
1829 		if (pd->p_len > 0 && (src->scrub->pfss_flags & PFSS_DATA_TS)) {
1830 			/*
1831 			 * Hey!  Someone tried to sneak a packet in.  Or the
1832 			 * stack changed its RFC1323 behavior?!?!
1833 			 */
1834 			if (pf_status.debug >= PF_DEBUG_MISC) {
1835 				DPFPRINTF(("Did not receive expected RFC1323 "
1836 				    "timestamp\n"));
1837 				pf_print_state(state);
1838 				pf_print_flags(th->th_flags);
1839 				kprintf("\n");
1840 			}
1841 			REASON_SET(reason, PFRES_TS);
1842 			return (PF_DROP);
1843 		}
1844 	}
1845 
1846 
1847 	/*
1848 	 * We will note if a host sends his data packets with or without
1849 	 * timestamps.  And require all data packets to contain a timestamp
1850 	 * if the first does.  PAWS implicitly requires that all data packets be
1851 	 * timestamped.  But I think there are middle-man devices that hijack
1852 	 * TCP streams immediately after the 3whs and don't timestamp their
1853 	 * packets (seen in a WWW accelerator or cache).
1854 	 */
1855 	if (pd->p_len > 0 && src->scrub && (src->scrub->pfss_flags &
1856 	    (PFSS_TIMESTAMP|PFSS_DATA_TS|PFSS_DATA_NOTS)) == PFSS_TIMESTAMP) {
1857 		if (got_ts)
1858 			src->scrub->pfss_flags |= PFSS_DATA_TS;
1859 		else {
1860 			src->scrub->pfss_flags |= PFSS_DATA_NOTS;
1861 			if (pf_status.debug >= PF_DEBUG_MISC && dst->scrub &&
1862 			    (dst->scrub->pfss_flags & PFSS_TIMESTAMP)) {
1863 				/* Don't warn if other host rejected RFC1323 */
1864 				DPFPRINTF(("Broken RFC1323 stack did not "
1865 				    "timestamp data packet. Disabled PAWS "
1866 				    "security.\n"));
1867 				pf_print_state(state);
1868 				pf_print_flags(th->th_flags);
1869 				kprintf("\n");
1870 			}
1871 		}
1872 	}
1873 
1874 
1875 	/*
1876 	 * Update PAWS values
1877 	 */
1878 	if (got_ts && src->scrub && PFSS_TIMESTAMP == (src->scrub->pfss_flags &
1879 	    (PFSS_PAWS_IDLED|PFSS_TIMESTAMP))) {
1880 		getmicrouptime(&src->scrub->pfss_last);
1881 		if (SEQ_GEQ(tsval, src->scrub->pfss_tsval) ||
1882 		    (src->scrub->pfss_flags & PFSS_PAWS) == 0)
1883 			src->scrub->pfss_tsval = tsval;
1884 
1885 		if (tsecr) {
1886 			if (SEQ_GEQ(tsecr, src->scrub->pfss_tsecr) ||
1887 			    (src->scrub->pfss_flags & PFSS_PAWS) == 0)
1888 				src->scrub->pfss_tsecr = tsecr;
1889 
1890 			if ((src->scrub->pfss_flags & PFSS_PAWS) == 0 &&
1891 			    (SEQ_LT(tsval, src->scrub->pfss_tsval0) ||
1892 			    src->scrub->pfss_tsval0 == 0)) {
1893 				/* tsval0 MUST be the lowest timestamp */
1894 				src->scrub->pfss_tsval0 = tsval;
1895 			}
1896 
1897 			/* Only fully initialized after a TS gets echoed */
1898 			if ((src->scrub->pfss_flags & PFSS_PAWS) == 0)
1899 				src->scrub->pfss_flags |= PFSS_PAWS;
1900 		}
1901 	}
1902 
1903 	/* I have a dream....  TCP segment reassembly.... */
1904 	return (0);
1905 }
1906 
1907 int
pf_normalize_tcpopt(struct pf_rule * r,struct mbuf * m,struct tcphdr * th,int off,sa_family_t af)1908 pf_normalize_tcpopt(struct pf_rule *r, struct mbuf *m, struct tcphdr *th,
1909     int off, sa_family_t af)
1910 {
1911 	u_int16_t	*mss;
1912 	int		 thoff;
1913 	int		 opt, cnt, optlen = 0;
1914 	int		 rewrite = 0;
1915 	u_char		 opts[TCP_MAXOLEN];
1916 	u_char		*optp = opts;
1917 
1918 	thoff = th->th_off << 2;
1919 	cnt = thoff - sizeof(struct tcphdr);
1920 
1921 	if (cnt > 0 && !pf_pull_hdr(m, off + sizeof(*th), opts, cnt,
1922 	    NULL, NULL, af))
1923 		return (rewrite);
1924 
1925 	for (; cnt > 0; cnt -= optlen, optp += optlen) {
1926 		opt = optp[0];
1927 		if (opt == TCPOPT_EOL)
1928 			break;
1929 		if (opt == TCPOPT_NOP)
1930 			optlen = 1;
1931 		else {
1932 			if (cnt < 2)
1933 				break;
1934 			optlen = optp[1];
1935 			if (optlen < 2 || optlen > cnt)
1936 				break;
1937 		}
1938 		switch (opt) {
1939 		case TCPOPT_MAXSEG:
1940 			mss = (u_int16_t *)(optp + 2);
1941 			if ((ntohs(*mss)) > r->max_mss) {
1942 				th->th_sum = pf_cksum_fixup(th->th_sum,
1943 				    *mss, htons(r->max_mss), 0);
1944 				*mss = htons(r->max_mss);
1945 				rewrite = 1;
1946 			}
1947 			break;
1948 		default:
1949 			break;
1950 		}
1951 	}
1952 
1953 	if (rewrite)
1954 		m_copyback(m, off + sizeof(*th), thoff - sizeof(*th), opts);
1955 
1956 	return (rewrite);
1957 }
1958